NATURAL WAXES 373 



lias a tliiekoncd portion consistinp; of outin, wliicli is a wax-like substance 

 impermeable to water. Plants indigenous to arid or desert sections have 

 especially well-developed cutinized areas on their leaves. Ordinarily, the 

 greatest development of the wax coat is on the under sui'faces of the 

 leaves, where the stomata or pores are most abundant. The wax appar- 

 ently serves largely to reduce the loss of moistiu'c by transpiration. Where 

 the rays of the sun are particularly intense, resins as well as waxes may serve 

 as protective agents. This is the case with the Coville creosote bush 

 (Larrea tridentata Vail.), and many other desert xerophytes. 



Wax sometimes forms over the whole leaf, as in the bog bilberry {Vac- 

 cinium uliginosimi L.), or sometimes only on the lower surface, as in the bog 

 rosemary {Andromeda polifoUa L.), the small cranberry (Vaccinium 

 oxycoccus L.), and many other shrubs and grasses. 



In some cases wax may be secreted over the entire plant to protect it 

 from water or saltiness, as is the case with the red swamp maple {Acei' 

 ruhrum L.). A wax coating is a prevailing feature of a number of halophytes 

 (salt-water plants). This proA'ides a glaucous or mat blue-green coating 

 for their leaves. Examples of this last category are the sea pea {Lathyrus 

 japonicus {ynaritimus) L.), the sea holly {Eryngium maritinmm L.), the sea 

 bluebell {Mertensia maritima L.), and the yellow horn poppy {Glaucium 

 flavum CvQXiiz) . 



Another common site for the deposition of wax is on the cuticles of fruits 

 and vegetables. It is particularly^ noticeable in grapes and plums, where it 

 is sometimes called the bloom. It may be present in the form of grains, 

 rods, or crusts. The function seems to be to prevent absorption of water as 

 it flows over the surface of the fruit. 



(a) Waxes from Plant Leaves and Stems. One may subdivide this group 

 into the following 5 subgroups: (1) waxes of palms, where the wax is more 

 abundant on the leaves than on other parts, as in the case of Copernicia 

 cerifera Mart., the source of carnauba wax; (2) waxes of shrubs and herbs 

 in which the wax is distributed over the entire plant, as in the wax slipper 

 flower, Pedilanthus pavonis Boiss., the source of candelilla wax; a wax also 

 called candelilla, but differing in constants, is obtained from the wax 

 euphorbia {Euphorhia antisyphilitica); (3) waxes of grasses and sedges, in 

 which the wax is principally on the stem, as in Saccharum officinarum L., 

 from which sugar-cane wax is deriA'ed; (4) waxes of broad-leaf trees, which 

 contain only small amounts; and (-5) waxes of narrow-leaf trees such as 

 conifers, from the essential oils of which waxes can be reco^•ered. 



a'. Carnauba Wax: One of the best known of the plant waxes is ob- 

 tained from the leaves of an American species of the palm, known as 

 Copernicia cerifera Martins. The natural habitat for this palm is Brazil 

 where it has a wide distribution through the semi-arid Brazilian Northeast. 

 Several varieties of carnauba palm abound throughout this area. The so- 



